The present invention is particularly related to a micro-lens array and a method for making the micro-lens array.
Numerous approaches have been utilized in the optical industry to make micro-lens arrays. Some conventional approaches have included an ink-jet process to deposit ultraviolet curable lens material on a base element, a hot embossing process to manufacture polycarbonate lenses, or a resist reflow process to pattern a spherical surface. Each of these conventional approaches has a disadvantage. For example, using an ink-jet process creates difficulty in tailoring the surface shape of the lens element. While spherical lenses may be easily formed through an ink-jet process, control of such a process is difficult for asymmetrically shaped lenses. Hot embossing causes significant material shrinkage after the embossing, which may lead to distorted reproduction. Using resist reflow is expensive and requires the use of clean room facilities.
Upon preparation of a master micro-lens array, replica lens arrays may be formed through molding techniques which are well known in the optical industry. See, for example, U.S. Pat. No. 6,300,464 (Morijiri et al.), U.S. Pat. No. 6,301,005 (Legrand et al.), and U.S. Pat. No. 6,129,866 (Hamanaka et al). Conventional replication approaches, however, have failed to address various issues necessary to be solved before the formed replicas can be used in a commercial product. Some important issues include control of distortion of the mold, material loss, environmental stability, and refractive index tailoring of the optical elements.
There exists a need for a low cost micro-lens array which addresses one or more of the disadvantages found in conventional approaches.
The invention provides a micro-lens array that includes a base element and a plurality of micro-lenses formed of a resin and including nanoparticles, wherein the micro-lenses have a hardness of greater than 70 on the D shore scale.
The invention further provides a method for forming replica micro-lens arrays from a master micro-lens array having a plurality of micro-lenses. The method includes the steps of applying an anti-stiction coating to a surface of the master micro-lens array and the micro-lenses, providing an elastomeric material over the surface of the master micro-lens array and the micro-lenses, curing the elastomeric material, removing the elastomeric material from the master micro-lens array, the elastomeric material having a plurality of cavities, filling the cavities with an epoxy, and curing the epoxy.
The invention further provides a replica micro-lens array assembly that includes a base element, a backing plate, and walls extending between the base element and the backing plate and encompassing a cavity, wherein a surface of the base element facing the cavity is coated with an anti-stiction material.
The invention also provides a method of preparing a resin containing nanoparticles. The method includes the steps of neutralizing nanoparticles, mixing the neutralized nanoparticles in isopropyl alcohol with a trialkoxysilane reagent to form a colloidal suspension of modified nanoparticles, removing excess trialkoxysilane reagent from the colloidal suspension of modified nanoparticles through dialysis, mixing the colloidal suspension of modified nanoparticles with a solvent, removing the isopropyl alcohol from the colloidal suspension of modified nanoparticles, and blending the colloidal suspension of modified nanoparticles with a photocurable resin.